In general, hydrogenated nitrile rubber is produced by the catalytic hydrogenation of the carbon-carbon double bonds contained in nitrile rubber. Vulcanizates of hydrogenated nitrile rubber are known to have excellent resistance to ageing in hot air or hot oil.
It is known to chemically modify hydrogenated nitrile rubber so as to produce a material having characteristics which are particularly well suited for a particular application. For example, U.S. Application Ser. No. 291,964 (filed 30 Dec. 1988, now U.S. Pat. No. 4,879,352) teaches the preparation of hydrogenated nitrile rubber having oxazoline functionality and U.S. Application Ser. No. 239,783 (filed 16 Sept.1988, now U.S. Pat. No. 4,868,881) teaches the preparation of an adduct of hydrogenated nitrile rubber and a halogen.
The modification of hydrogenated nitrile rubber often leads to a polymer which has a high gel content (i.e. as measured by the amount of polymer which is insoluble in methyl ethyl ketone). Polymers having high gel content are normally considered undesirable because they do not mix well with compounding ingredients and because they are difficult to vulcanize.
It is an object of the present invention to prepare an adduct of a hydrogenated nitrile rubber and a sulfenyl chloride, which adduct is characterized by having a gel content of less than 15 per cent.